High-gain GaAs photoconductive semiconductor switches: measurement of filament velocity and reduced trigger energy

摘要

The time evolution of the current filaments in an optically triggered, high gain GaAs switch was studied by recording the infrared photoluminescence from the filaments. When the switch is triggered with two laser diode arrays (through a fiber optic) that are activated within 1 ns of each other, two current filaments are observed, each one emanating from the point of illumination. By delaying one laser with respect to the other, the evolution of the filament was recorded in a time resolved fashion. The first filament that is triggered crosses the switch, the voltage drops and the other filament ceases to grow. By varying the delay between the trigger lasers, the tip velocity is measured to be up to 5.9 $POM 1 $MUL 10$+9$/ cm/s. This speed is 600 times larger than the peak drift velocity of carriers in GaAs. This observation supports switching models that rely on carrier generation at the tip of the filament. The filaments speed up as they cross the switch: for one voltage range initial speeds were 0.7 $POM 1 $MUL 10$+9$/ cm/s and final speeds (the last 100 ps of motion) exceed 5.5 $POM 1 $MUL 10$+9$/ cm/s. This experiment also shows a relationship between the rise time of the voltage across the switch and the required trigger energy and switch jitter.